I like how easy this tool makes creating my own API's very simple! The code snippets are great too because they're so well written you can use them straight away without having any issues translating into your language or environment (I'm using PHP).
Maybe give an option where we could create our "own" topics as opposed with being pushed ones? For example one topic per client would be nice but that might take up some space within each channel which isn't always possible when dealing big companies who have multiple channels open at once etc..